Three-dimensional Numerical Analysis on Acoustic Properties of Double-porosity Materials

• Main Authors: Tz-HengLin, 林子恆
• Other Authors: Yu-Yun Lin
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/a67duy

碩士 === 國立成功大學 === 土木工程學系 === 105 === Most sound absorption materials are generally low density and high porosity, such as rockwool and glasswool. To improve the ability of sound absorption at low to medium frequencies, these porous materials are added meso-pores of size much bigger than the characteristic length of original micro-pores, as so-called double-porosity materials. Double-porosity materials can effectively improve the sound absorbing performance at specific frequency range, because of the coupling of meso-pores and micro-pores also referring to as pressure diffusion phenomenon. However, double-porosity materials behaves poorly in sound insulation. This research studied how the porosity and geometry of meso-pores improve the ability of double-porosity materials in sound absorption and insulation. Three-dimensional acoustic numerical models were developed using the finite element software Comsol. Several equivalent fluid models and Biot model were used as comparison. Biot model describes the acoustic vibration of solid skeleton and pore fluid, so it is more convenient to use in both sound absorption and insulation analyses than equivalent fluid models. From the comparison of numerical results and experimental data in the literature, the improvement in sound absorption for double-porosity materials can be predicted. Using different porosity and characteristic length of meso-pores, the effective frequency range can be adjusted. However, as the meso-porosity increases, the sound insulation performance will be reduced. Because the sound insulation is dominated by mass and flow resistivity per unit area.